Labour MP Chris Williamson has apologised for tweeting in support of a jazz musician his own party called a "vile anti-Semite".
Islington Council had banned saxophonist Gilad Atzmon from playing with Ian Dury's old band the Blockheads at the Islington Assembly Hall.
The council said Mr Atzmon's appearance "might harm" relationships with the London borough's religious communities.
The MP had posted a link to a petition calling for him to be reinstated.
In his post, Mr Williamson, a former shadow minister and close ally of Jeremy Corbyn, said: "Hands off Gilad Atzmon - sign the petition!"
He deleted the message and posted an apology after social media users and Jewish groups expressed their anger.
"Earlier today I tweeted a petition about an Islington Council ban against the Blockheads performing with their chosen line-up. The council has blocked jazz musician Gilad Atzmon from playing with the group," said the Derby North MP.
"Since then I've learned that Atzmon, a former Israeli soldier, is not confined to the jazz world. I am told that in various blogs and in speeches he has adopted anti-Semitic language.
"I wasn't aware of this until after I tweeted the petition. As soon as I was informed, I deleted the tweet. I've always condemned all forms of racism, including anti-Semitism, and strongly disassociate myself from Atzmon's anti-Semitic views.
"I therefore apologise for tweeting this petition and any distress or offence it may have caused."
APOLOGY— Chris Williamson MP #GTTO (@DerbyChrisW) December 21, 2018
Earlier today I tweeted a petition about an Islington Council ban against the Blockheads performing with their chosen line up. The council has blocked jazz musician Gilad Atzmon from playing with the group.
Despite Mr Williamson's apology, the Jewish Labour Movement called for Mr Williamson to be suspended from the party.
The campaign group Labour Against Antisemitism tweeted in support of the Jewish Labour Movement, adding: "There can be no equivocation: Chris Williamson MP must have his membership of Labour withdrawn today."
A Labour spokesman said: "Gilad Atzmon is a vile anti-Semite. Chris Williamson has said he was not aware of Atzmon's appalling views and rightly apologised for his tweet."
Labour MP Wes Streeting tweeted: "Chris has now apologised, as he should.
"Presumably it was just a love of jazz that led him to sign and share a petition defending someone with anti-Semitic form - apparently without even checking why the Council (a LABOUR Council) took the step of banning him in the first place."
Speaking to the Islington Gazette, Mr Atzmon accused the council of having "adopted the role of book burners".